Copper(II)/diiminic complexes based on 2-hydroxybenzophenones: DNA- and BSA-binding studies and antitumor activity against HCT116 and HepG2 tumor cells

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Here, we report four new heteroleptic Cu(II) complexes with the formula [Cu(bipy)(2H4MeBz)]NO3 (1), [Cu(phen)(2H4MeBz)]NO3 (2), [Cu(bipy)(2H4OcBz)]NO3 (3) and [Cu(phen)(2H4OcBz)]NO3 (4), where the ligands are 2-hydroxy-4-methoxybenzophenone (2H4MeBz), 2-hydroxy-4-(octyloxy)benzophenone (2H4OcBz), 2,2′-bipiridine (bipy) and 1,10-phenantroline (phen). All compounds present two bidentate ligands, a monoanionic 2-hydroxybenzophenone, forming a six-membered chelate ring and the diiminic ring forming a five-membered chelate ring, as well as one nitrate as counterion located at the axial position, as suggested by the crystal structure of complex 2. Complex/DNA interaction studies were also performed using spectroscopic titration (Kb close to 104 M−1), viscosity, Hoechst 33258 competition, and circular dichroism, revealing a moderate interaction between them. Additionally, complexes 1–4 moderately interact with BSA (Bovine Serum Albumin). The compounds were evaluated against HCT116 (human colon carcinoma) and HepG2 (human hepatocellular carcinoma) cancer cells and against MRC-5 (human lung fibroblast), a noncancer cells. The cytotoxic results suggest that complexes 2 and 4 are more cytotoxic than 1 and 3, showing that the presence of phen ligand may play an important role in increasing the biological effect of the compounds.